Fuels and Burners for Domestic Heating

Discusses fuels and burners for domestic heating, including hand-fired coal or coke, automatic coal stoker, gas-fired heaters, oil burners. INlcudes table of comparative fuel costs

Crack paths under mixed mode loading

Long fatigue cracks that initially experience mixed mode displacements usually change direction in response to cyclic elastic stresses. Eventually the cracks tend to orient themselves into a pure mode I condition, but the path that they take can be complex and chaotic. In this paper, we report on recent developments in techniques for tracking the crack path as it grows and evaluating the strength of the mixed mode crack tip stress field

Vertex Cover Kernelization Revisited: Upper and Lower Bounds for a Refined Parameter

An important result in the study of polynomial-time preprocessing shows that there is an algorithm which given an instance (G,k) of Vertex Cover outputs an equivalent instance (G',k') in polynomial time with the guarantee that G' has at most 2k' vertices (and thus O((k')^2) edges) with k' <= k. Using the terminology of parameterized complexity we say that k-Vertex Cover has a kernel with 2k vertices. There is complexity-theoretic evidence that both 2k vertices and Theta(k^2) edges are optimal for the kernel size. In this paper we consider the Vertex Cover problem with a different parameter, the size fvs(G) of a minimum feedback vertex set for G. This refined parameter is structurally smaller than the parameter k associated to the vertex covering number vc(G) since fvs(G) <= vc(G) and the difference can be arbitrarily large. We give a kernel for Vertex Cover with a number of vertices that is cubic in fvs(G): an instance (G,X,k) of Vertex Cover, where X is a feedback vertex set for G, can be transformed in polynomial time into an equivalent instance (G',X',k') such that |V(G')| <= 2k and |V(G')| <= O(|X'|^3). A similar result holds when the feedback vertex set X is not given along with the input. In sharp contrast we show that the Weighted Vertex Cover problem does not have a polynomial kernel when parameterized by the cardinality of a given vertex cover of the graph unless NP is in coNP/poly and the polynomial hierarchy collapses to the third level.Comment: Published in "Theory of Computing Systems" as an Open Access publicatio

Nitrogen Retention in Headwater Streams: The Influence of Groundwater-Surface Water Exchange

Groundwater-surface water (GW-SW) interaction lengthens hydraulic residence times, increases contact between solutes and biologically active surfaces, and often creates a gradient of redox conditions conducive to an array of biogeochemical processes. As such, the interaction of hydraulic patterns and biogeochemical activity is suspected to be an important determinant of elemental spiraling in streams. Hydrologic interactions may be particularly important in headwater streams, where the extent of the GW-SW mixing environment (i.e., hyporheic zone) is proportionately greater than in larger streams. From our current understanding of stream ecosystem function, we discuss nitrogen (N) spiraling, present a conceptual model of N retention in streams, and use both of these issues to generate specific research questions and testable hypotheses regarding N dynamics in streams

Perceptions of status and TMO workgroup cooperation: implications for project governance

Achieving and sustaining the cooperation of individuals with their temporary multi-organization (TMO) workgroups is, arguably, one of the most enduring challenges facing the construction sector. A mediational model connecting pride and self-respect to each of four dimensions of cooperative behaviour-in-role, compliance, extra-role, and deference-is tested in a survey sample of 140 construction professionals in Hong Kong. Bootstrap tests of the indirect effect of pride on cooperative behaviour suggest that self-respect fully mediates the influence of pride on in-role behaviour and compliance behaviour, and partially mediates the influence of pride on extra-role behaviour. The results also suggest that pride has no effect on deference behaviour. While needing corroboration by future research, the findings suggest that viable strategies designed to foster pride and self-respect could engender and sustain cooperation in construction TMO workgroups, and support ongoing efforts to reform construction. The bootstrapping procedures for testing intervening variable models are elaborated in the hope that this will encourage more process analysis research in construction. © 2012 Copyright Taylor and Francis Group, LLC

Fuels and Burners

Discusses fuels and burners for domestic heating, including hand-fired coal or coke, automatic coal stoker, gas-fired heaters, oil burners. INlcudes table of comparative fuel costs

Fuels and Burners

Discusses fuels and burners for domestic heating, including hand-fired coal or coke, automatic coal stoker, gas-fired heaters, oil burners. INlcudes table of comparative fuel costs

Preparation, characterization, and decay of einsteinium(II) in the solid state

Pour la première fois, des échantillons de EsCl2, EsBr2 et EsI2 ont été préparés par réduction des trihalogénures d'einsteinium correspondants par de l'hydrogène à des températures élevées. Les trois dihalogénures ont été caractérisés principalement par leurs spectres d'absorption. Les produits de décroissance d'échantillons de EsX2 maintenus à la température ambiante et à la température de l'hélium liquide ont été suivis par spectrophotométrie. Dans tous les cas, l'identification positive des espèces petit-fils, CfX2, a été faite. Aucune preuve spectrale définitive de la présence possible du produit fils BkX2 n'a été obtenue.Samples of EsCl2, EsBr2, and EsI2 have been prepared for the first time by reduction of the corresponding einsteinium trihalides with hydrogen gas at elevated temperatures. The three dihalides were characterized primarily by their absorption spectra. The products of the decay of EsX2 samples held at ambient and liquid helium temperatures have been monitored by spectrophotometry. In all cases positive identification of the granddaughter, CfX2, species has been made. No definite spectral evidence for the presence of the possible daughter products, BkX2, has been obtained